The present application is generally related to a steering system, such as an electric power steering (EPS) system that detects near-limit vehicle conditions such as an understeer condition and oversteer condition, and that in response adjusts the torque assist that is provided to a driver.
Typically, vehicles today are equipped with a steering system such as an Electric Power Steering (EPS) system. The EPS system assists a driver to steer the vehicle in desired direction. For example, the EPS system generates an assist torque during the maneuvers to facilitate overcoming one or more forces acting on the vehicle, such as surface friction. Various driving maneuvers and environment condition (e.g. low friction surface) can lead to one or more tire forces reaching near-limit conditions. Vehicles can have undesired yaw behavior in such conditions. Such a behavior is often described as an understeer condition (vehicle yawing less than desired) or an oversteer condition (vehicle yawing more than desired). Although the society of automotive engineers (SAE) has defined such conditions in steady state situations, the situations occur in both steady state and transient (dynamic) state. Typically, electronic stability control uses selective braking and other techniques to control vehicle when understeer or oversteer conditions are detected. However, such techniques are reactive to driver maneuvers in the understeer and oversteer conditions.
Accordingly, it is desirable to improve the steering system by proactively assisting the driver with maneuvers in case of vehicle motion states such as the understeer and oversteer conditions.